This invention relates to a vehicle driven by an engine using LPG (liquefied petroleum gas) as fuel, and more particularly to a system to shut off the supply route of the LPG fuel to the engine except when the engine is operating.
In FIG. 1, a typical prior-art fuel system for vehicles exclusively using LPG fuel is shown schematically. As shown in FIG. 1, the LPG fuel flows under pressure from an LPG tank 1 through a filter 2 into a regulator 3, where it is then decompressed to be vaporized, and this vaporized fuel is sucked in the engine 6 from a sow LPG hose 4 through a carburetor 5. A solenoid valve 7 is interposed in the LPG supply route between the LPG tank 1 and the regulator 3. This valve 7 can be opened and closed by manipulating a fuel switch 11 on an instrument panel after turning an ignition switch 10 on, whereby the LPG fuel can be supplied or cut off.
In the above described conventional fuel system, there is a danger that the LPG fuel may, under its own vapor pressure, flow toward the engine 6 and escape from the carburetor 5 to the outside through the air cleaner in spite of the engine being stopped, because the solenoid valve 7 opens when both the ignition switch 10 and the fuel switch 11 are turned on. Further, if the temperatures in the combustion chambers of the engine 6 are higher than the spontaneous combustion temperature of the LPG, the engine 6 may start by the ignition switch 10 only being switched on while the fuel switch 11 is also switched on and hence the vehicle may suddenly lurch out.